October 15, 2001
The state of Washington’s Department of Fish and Wildlife reported in August that at least 1.6 million wild chinook salmon fry died last spring after being stranded in gravel by low-water conditions along a 17-mile stretch of the Columbia River.
The estimate of fry mortality in a section of the Columbia River downstream from Priest Rapids Dam is about 16 times greater than in the previous two years, said Rod Woodin, WDFW Columbia River policy coordinator.
“Drought, together with fluctuations in water levels caused by dam operations, took a heavy toll on emerging mid-Columbia fall chinook salmon fry this year,” said Woodin. “How those losses will be reflected in adult returns three and four years from now remains to be seen,” he said.
Woodin said low-water conditions caused by this year’s drought amplified the effect of fluctuations in water levels resulting from dam operations.
“Actually, fluctuations in water levels from dam operations were much less than in previous years,” Woodin said. “The problem is that any variation during a low-water year ‘de-waters’ a much greater area than when the river is at a normal level.”
Since 1999, estimates of fry mortality on 17 miles of the Columbia River below Priest Rapids Dam have been an integral part of the Hanford Reach Juvenile Fall Chinook Protection Program, an inter-jurisdictional, flow-management and monitoring effort involving WDFW, federal natural resource agencies, area treaty tribes and local dam operators.
As in the past two years, this year’s monitoring effort was conducted in spring when emerging salmon fry are most susceptible to fluctuations in water levels. Technicians walked the riverbanks between April 1 and June 10 to locate stranded fish.
When water levels drop, thousands of fry can be found along the riverbank or stranded in shallow pools where the water temperature often reaches lethal levels, said Paul Hoffarth, WDFW’s lead biologist on the project.
“The monitoring crews try to salvage as many of them as they can, but that usually amounts to a small fraction of what’s there,” Hoffarth said.
Hoffarth noted that the loss of 1.6 million fry in the monitored area represents about 7 percent of the year’s total estimated fall chinook fry production. But that may account for only a small portion of the fry mortalities, he said.
“These estimates do not account for fry that die elsewhere in the 51-mile Hanford Reach or further down river,” Hoffarth said. “This is clearly a tough year for juvenile fall chinook on the mid-Columbia River,” he added.
The Hanford Reach supports the largest wild fall chinook population in the main stem Columbia River and is a primary contributor to sport, commercial and tribal fisheries.
Drought conditions
Soaring August temperatures combined with below-normal precipitation have exacerbated extremely dry conditions throughout the state. In central Washington, precipitation is just 3 percent of average for the month, and only 75 percent for the year.
“The effects of these conditions are dramatic, particularly on the east side of the Cascades where tinder-dry conditions are contributing to lightening-sparked fires throughout the region,” said Doug McChesney, drought coordinator for Washington’s Department of Ecology.
Although significant rains were predicted to fall across the state in late August, this rain wasn’t expected to help most streams, which are fed by groundwater at this time of year. “We’re not likely to see measurable improvements in these streams until early fall,” McChesney said.
For the first time in many years, the Department of Ecology told about 150 water-right holders on the Little Spokane River to stop withdrawing water because of low water levels.
Record low flows are being set almost daily on one or more rivers in Washington. Real-time information about river flows may be found by visiting this U.S. Geological Survey Web site.
Strong chum salmon returns expected
This month, WDFW biologists are reporting “outstanding” salmon returns that have marked most of 2001 are expected to continue with the strongest returning Puget Sound chum salmon run in three years.
Pre-season forecasts predict 730,000 to 880,000 fall and winter chum salmon are headed back to Puget Sound in November and December.
The chum support a variety of sport, commercial and tribal fisheries, including a popular Hood Canal recreational fishery, where 225,000 to 375,000 chum are expected to return.
Although the run is the highest in recent years, it is not expected to rival peak returns in the last two decades. Between 1978 and 1998, Puget Sound chum runs exceeded one million fish 17 times and broke the two million mark three times. The lower recent numbers are believed to be due to changes in conditions in the north Pacific Ocean.
“The recent contraction in chum salmon run sizes reflects normal long-term cycles in regional stocks, not an overall decline to depressed status,” said Travis Nelson, WDFW stock assessment biologist.
More information about chum salmon may be found on this WDFW Web page, featuring information on chum management, life history and identification, and regional reports for Puget Sound, coastal areas and the Columbia River.